a

#include <stdio.h>
#include <stdlib.h>

int vis[100][100];
int visi[100];
int fin[100];
int fini=0;
int finn[100];
int finni = 0;

struct node {
    int v;
    struct node* next;
};

struct nodeArray {
    struct node* head;
};

struct graph {
    int S;
    struct nodeArray* array;
};

struct graph* initializeGraph(int n) {
    struct graph* g = (struct graph*) malloc(sizeof(struct graph));
    g->S = n;
    g->array = (struct nodeArray*) malloc(n*sizeof(struct nodeArray));
    for(int i =0; i<n; i++) {
        g->array[i].head = NULL;
    }
    return g;
}

void addEdge(struct graph* g, int j, int k) {
    struct node* a = (struct node*) malloc(sizeof(struct node));
    a->v = k;
    a->next = g->array[j].head;
    g->array[j].head = a;
    
    struct node* b = (struct node*) malloc(sizeof(struct node));
    b->v = j;
    b->next = g->array[k].head;
    g->array[k].head = b;
}

void traverse(struct graph* g, int j, int k) {
    visi[j] = 1;
    struct node* temp = g->array[j].head;
    while(temp) {
        if(vis[j][temp->v]==0) {
            vis[j][temp->v]=1;
            vis[temp->v][j] = 1;
            traverse(g,temp->v,k);
            fin[fini++] = j;
            finn[finni++] = temp->v;
        }
        temp = temp->next;
    }
}

int main()
{
    int n,m;
    scanf("%d%d",&n,&m);
    struct graph* g = initializeGraph(n);
    for(int i = 0; i<m; i++) {
        int j,k;
        scanf("%d%d",&j,&k);
        addEdge(g,j,k);
    }
    
    traverse(g,0,n);
    for(int i = 0; i<n; i++) {
        if(visi[i]==0) { 
            printf("-1");
            return 0;
        }
    }
    for(int i = fini-1; i>=0; i--) {
        printf("%d->%d\n",fin[i],finn[i]);
    }
    return 0;
}